Novel technique to synthesize AFX-type zeolite using a bulky and rigid diquaternary ammonium cation
Novel technique to synthesize AFX-type zeolite using a bulky and rigid diquaternary ammonium cation
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使用大体积刚性双季铵阳离子合成 AFX 型沸石的新技术
DOI：
10.1166/apm.2016.1114
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Y. Kubota
中科院分区：
文献类型：
--
作者：
N. Nakazawa;S. Inagaki;Y. Kubota
具有大空腔的小孔沸石由于最近开发的工业应用，特别是例如甲醇或二甲醚制烯烃（MTO或DTO）反应和NOx的选择性催化还原（SCR）而引起极大关注。与众所周知的CHA型沸石相反，具有8-环通道和细长的大空腔（AFT笼）的AFX型沸石尚未应用于这种方法，这是由于窄的合成窗口引起的有限的Si/Al组成范围。本工作首次将一种已知可合成MSE型分子筛的大体积刚性N，N，N，'N'-四乙基双环[2.2.2]辛-7-烯-2，3：5，6-二吡咯烷鎓（TEBOP ~（2+））二价阳离子用于合成AFX型分子筛，成功地拓宽了合成窗口。产物Si/Al摩尔比在6和9之间的范围内以及基于二六面体的颗粒形态是在常规AFX型沸石中从未观察到的显著特征。这种新型AFX型沸石的结晶可以理解的基础上的客体/主体之间的关系的OSDA和AFX中的笼结构。与AFX型沸石具有相当大的结构相似性的FAU型沸石作为起始材料对于结晶是必需的。除了潜在的工业应用，结晶动力学的调查也进行了讨论。
Small pore zeolites with large cavities have greatly attracted attention because of recently-developed industrial applications especially such as methanol or dimethyl ether-to-olefin (MTO or DTO) reaction and selective catalytic reduction (SCR) of NOx. AFX-type zeolites, possessing 8-ring channels and elongated large-cavity (AFT cage), have not been applied to such processes contrary to wellknown CHA-type zeolites due to the limited Si/Al composition range which arises from a narrow synthesis window. In this work, a bulky and rigid N,N,N,'N'-tetraethylbicyclo[2.2.2]oct-7-ene-2,3:5,6-dipyrrolidinium (TEBOP2+ dication, which is already known to give MSE-type zeolites, was firstly used to synthesize AFX-type zeolites and successfully widen the synthesis window. The product Si/Al molar ratio in the range between 6 and 9 and the dihexahedron-based particle morphology are the remarkable features which have never been observed in conventional AFX-type zeolites. Crystallization of this novel AFX-type zeolite can be understandable based on guest/host relationship between the OSDA and the cage structure in AFX. An FAU-type zeolite, which has the considerable structural similarity with an AFX-type zeolite, is essential for the crystallization as a starting material. In addition to potentials for industrial applications, an investigation of crystallization kinetics is also discussed.